Aerial pesticide application causes DNA damage in pilots from Sinaloa, Mexico.

The use of pesticides in agricultural production originates residues in the environment where they are applied. Pesticide aerial application is a frequent source of exposure to pesticides by persons dedicated to agricultural practices and those living in neighboring communities of sprayed fields. The aim of the study was to assess the genotoxic effects of pesticides in workers occupationally exposed to these chemicals during their aerial application to agricultural fields of Sinaloa, Mexico. The study involved 30 pilots of airplanes used to apply pesticides via aerial application and 30 unexposed controls. Damage was evaluated through the micronucleus assay and by other nuclear abnormalities in epithelial cells of oral mucosa. The highest frequency ratios (FR) equal to 269.5 corresponded to binucleated cells followed by 54.2, corresponding to cells with pyknotic nuclei, 45.2 of cells with chromatin condensation, 3.7 of cells with broken-egg, 3.6 of cells with micronucleus, and 2.0 of karyolytic cells. Age, worked time, smoking, and alcohol consumption did not have significant influence on nuclear abnormalities in the pilots studied. Pesticide exposure was the main factor for nuclear abnormality results and DNA damage. Marked genotoxic damage was developed even in younger pilots with 2 years of short working period, caused by their daily occupational exposure to pesticides.

First Report of Powdery Mildew (Podosphaera pannosa) of Roses in Sinaloa, Mexico.

Rose (Rosa spp.) is the most important ornamental plant cultivated in greenhouse and open fields in Mexico but its quality has been limited by powdery mildew (PM). High incidence and disease damage is common during winter in Sinaloa, Mexico (temperature range 18 to 25°C and prolonged episodes of relative humidity ≥90%). The fungus attacks leaves and flowers and grows abundantly on the pedicels, sepals, and receptacles, especially when the flower bud is unopened (2). Field advisors in Mexico have referred to Sphaerotheca pannosa (Wallr. ex Fr.) Lév. as a causal agent of the disease. However, there has not been solid scientific evidence to support this statement. Morphometric and molecular analysis were conducted to elucidate the identity of the fungal isolates collected from 2012 through 2013 in northern Sinaloa. PM specimens included eight different rose varieties. Conidiophores and conidia were observed under a compound microscope. The mycelium had a mean diameter of 4.7 to 6.0 µm; conidiophores (Euoidium type) 2 to 5 celled, occasionally 6 celled emerged from the superficial mycelium; conidiophores were unbranched with conidia produced in chains from the apex. The average length of the conidiophores was 54.9 to 98.0 µm; the foot cell of the conidiophores was straight and was 24.9 to 53.6 µm long with a diameter from 8.2 to 9.8 µm across its medium part. Conidia originated from unswollen conidiogenous cells, with fibrosin bodies, formed in long chains, and were cylindrical to ovoid, 25.8 to 30.4 µm long and 13.9 to 17.3 µm wide. The outline of the conidial chains was crenate. Conidia exhibited a slight constriction at one end. The germ tubes emerged from a shoulder of the conidia. The outer wall of partially collapsed conidia showed longitudinal and transversal wrinkling and slight constrictions at the ends; the terminal end of the conidia was concentrically ridged. For molecular characterization, the ITS region of the specimens was amplified with primers ITS1F and ITS4. Phylogenetic analysis was performed with MEGA 6.0 (bootstrap = 1,000) using Kimura 2 parameter (K2P) substitution model. The resulting phylogeny grouped our specimens (GenBank KM001665 to 69) within a clade of Podosphaera pannosa (Wall.: Fr.) de Bary (formerly known as Sphaerotheca pannosa) sequences (e.g., AB525938; bootstrap (1,000) = 98). Phylogenetic and morphometric data are in agreement with descriptions of the anamorphic P. pannosa (1,3). Morphological studies indicate that P. macularis (previously known as S. humuli) and P. pannosa are not indistinctly different (2). Phylogenetic analysis showed relationship to P. pannosa, but not to P. macularis. Typical symptoms caused by P. pannosa were observed. Morphological studies (4) reported the anamorph of P. pannosa on Rosa spp. in central Mexico. To date, no report exists on the molecular identification of P. pannosa associated to roses in northern Sinaloa, Mexico. Future research directions should focus on finding the teleomorph of the fungus to support its identity, and to explore disease management tools such as effective fungicides and developing resistant rose cultivars. References: (1) U. Braun et al. Page 13 in: The Powdery Mildews: A Comprehensive Treatise. APS Press, St. Paul, MN, 2002. (2) R. K. Horst. Compendium of Rose Diseases. APS Press, St. Paul, MN, 1983. (3) L. Leus et al. J. Phytopathol. 154:23, 2006. (4) Yañez-Morales et al. Some new reports and new species of powdery mildew from Mexico. Schlechtendalia 19:46, 2009.

First Report of Powdery Mildew (Pseudoidium anacardii) of Mango Trees in Sinaloa, Mexico.

Powdery mildew of mango is an important disease in Mexico's northern Sinaloa state. Identification of the causal fungal agent has been hindered by the absence of information regarding its teleomorph, as well as a detailed morphometric analysis of the anamorph and molecular characterization. The first symptoms of the disease appear in mango inflorescences of early February, and it subsequently affects young fruits. The disease progresses during March and early April, causing significant fruit abortion and a scabby appearance in a high percentage of fruits that remain attached to the trees. We observed the disease on inflorescences but not in leaves during our sampling period. Powdery mildew specimens were collected during 2011 and 2012 and included Kent and Keith varieties from commercial orchards, and creole materials from backyards of private residences in the Ahome and Fuerte Counties of northern Sinaloa, Mexico. Symptomatic inflorescences were analyzed morphologically. Conidiophores and conidia were prepared by touching the whitish lesions with clear adhesive tape, which was then placed over microscope slides with a drop of distilled water and observed under a compound microscope. The anamorph structures of the pathogen were measured. The mycelium was septate and ramified on the surface of the host, forming a dense coat of branching hyphae. The mycelium had a diameter of 2.5 to 8.7 µm; conidiophores (Pseudoidium type) emerged from the superficial mycelium, were unbranched, and consisted of 1 to 3 cells with conidia forming singly from the apex. The length of the conidiophores varied from 30.0 to 77.5 µm; the foot cell of the conidiophores was straight, 10.0 to 47.5 µm long and with a diameter of 5.0 to 15.5 µm across its midpoint. Conidia without fibrosin bodies were borne singly, and were ellipsoid/ovoid, 22.5 to 46.2 µm long and 15.0 to 27.5 µm wide. Eighty percent of the germ tubes were forked (lobed); the rest were simple, emerged from the end, and were occasionally on the side of the conidia. Germ tubes ranged from 2.0 to 7.2 µm at the midpoint. The surface of the conidia appeared smooth under the scanning electron microscope, and elliptical conidia appeared constricted at their ends; this, however, was not observed in the ovoid conidia. In both cases, the terminal end of the conidia was smooth. The teleomorph was not found. Molecular and phylogenetic analysis of the ITS rDNA (2) region showed that samples are closely related to specimens of Pseudoidium anacardii (1) (teleomorph: Erysiphe quercicola [4]) collected from mango trees in diverse countries. Measurements of somatic and asexual structures are in agreement with descriptions of P. anachardii (formerly known as Oidium mangiferae) from India (3). The nucleotide sequences derived from this research were deposited in GenBank (Accession Nos. JX893951 to JX893957). To our knowledge, this is the first report of P. anacardii associated to mango inflorescences in Sinaloa, Mexico. Due to the economic importance of powdery mildew of mango trees in Sinaloa, future research directions should focus on finding the teleomorph of the fungus to support its identity. References: (1) U. Braun and R. T. A. Cook CBS Biodiversity Series No. 11, 2012. (2) S. Limkaisang et al. Mycoscience 47:327, 2006. (3) O. Prakash and K. C. Srivastava. Mango diseases and their management. A World Review Today and Tomorrow Publishers. New Delhi, India, 1987. (4) S. Takamatsu et al. Mycol. Res. 111:809, 2007.

Tomato infectious chlorosis virus Associated with Tomato Diseases in Baja California, Mexico.

Tomato (Solanum lycopersicum L.) is an important vegetable crop in Mexico. The national production in 2009 was 2,043,814 metric tons with a value of $163,560,636 US. Since 2007, abnormal yellow and crispy leaves were observed in commercial tomato fields in Ensenada County, Baja California, Mexico. In affected fields from two localities (San Quintín Valley and Ensenada), symptomatic plants were randomly distributed and symptoms resembled previous descriptions of crinivirus infections in tomato (3). The symptoms and the presence of whiteflies (Bemisia tabaci and Trialeurodes vaporariorum) in the affected fields suggested a viral etiology. Leaf samples of 143 symptomatic tomato plants were collected in the 2007 and 2008 growing seasons. Total RNA was extracted and analyzed by reverse transcription (RT)-PCR assay for simultaneous detection of Tomato infectious chlorosis virus (TICV) and Tomato chlorosis virus (ToCV). Degenerate primers (HS-11/HS-12) were used in combination with specific primers (TIC-3/TIC-4 and ToC-5/ToC-6) for detection of these viruses by nested-PCR (2). A PCR fragment of the expected size for TICV (223 bp) was amplified in 26 of 143 samples. None of the samples tested positive for ToCV. In addition, considering that whiteflies are vectors of begomoviruses, samples were also tested for presence of viral DNA. Results showed 30 positive samples and one with mixed infection. It is therefore possible that the viral disease symptoms observed could be caused in part by viruses other than TICV. Three amplicons from RT-PCR of tomato samples were cloned into the pGEM-T easy vector system II (Promega Corporation, Madison, WI) and sequenced. The sequence of one amplicon (GenBank Accession No. FJ609651) was compared with the sequences of other criniviruses reported in the NCBI/GenBank database using the Clustal V alignment method of the sequence analysis software suite Lasergene (MegAling, DNASTAR Inc., Madison, WI). Sequence analysis of the 223-bp PCR fragment corresponding to TICV showed 99.1% identity with a TICV isolate from Japan (GenBank Accession No. AB085602) and 100% identity with TICV isolates from the United States (GenBank Accession No. TIU67449). Although the presence of another crinivirus, ToCV, was reported previously in Mexico associated with tomato crops and two native weeds, S. nigrescens and Datura stramonium (1), this virus was not detected in Baja California during the present work. To our knowledge, this is the first report of TICV associated with tomato diseases in Mexico. The emerging of a previously unreported virus disease in tomato production areas of Mexico complicates disease management efforts. References: (1) P. Álvarez-Ruíz et al. Plant Pathol. 56:1043, 2007. (2) C. I. Dovas et al. Plant Dis. 86:1345, 2002. (3) G. C. Wisler et al. Plant Dis. 82:270, 1998.

Spatial Analysis of Phytophthora infestans Genotypes and Late Blight Severity on Tomato and Potato in the Del Fuerte Valley Using Geostatistics and Geographic Information Systems.

ABSTRACT Genetic structure of Phytophthora infestans, the causal agent of potato and tomato late blight, was analyzed spatially in a mixed potato and tomato production area in the Del Fuerte Valley, Sinaloa, Mexico. Isolates of P. infestans were characterized by mating type, allozyme analysis at the glucose-6-phosphate isomerase and peptidase loci, restriction fragment length polymorphism with probe RG57, metalaxyl sensitivity, and aggressiveness to tomato and potato. Spatial patterns of P. infestans genotypes were analyzed by geographical information systems and geo-statistics during the seasons of 1994-95, 1995-96, and 1996-97. Spatial analysis of the genetic structure of P. infestans indicates that geographic substructuring of this pathogen occurs in this area. Maps displaying the probabilities of occurrence of mating types and genotypes of P. infestans, and of disease severity at a regional scale, were presented. Some genotypes that exhibited differences in epidemiologically important features such as metalaxyl sensitivity and aggressiveness to tomato and potato had a restricted spread and were localized in isolated areas. Analysis of late blight severity showed recurring patterns, such as the earliest onset of the disease in the area where both potato and tomato were growing, strengthening the hypothesis that infected potato tubers are the main source of primary inoculum. The information that geostatistical analysis provides might help improve management programs for late blight in the Del Fuerte Valley.

Temporal and Spatial Patterns of Genetic Structure of Phytophthora infestans from Tomato and Potato in the Del Fuerte Valley.

ABSTRACT The temporal and spatial patterns of Phytophthora infestans population genetic structure were analyzed in the Del Fuerte Valley, Sinaloa, Mexico, during the crop seasons of 1994 to 1995, 1995 to 1996, and 1996 to 1997 by geographical information systems. Isolates of P. infestans were obtained from infected tissue of tomato and potato collected from two areas: (i) where both potatoes and tomatoes are grown, and (ii) where only tomatoes are grown. The isolates were characterized by mating type, allozymes at the glucose-6-phosphate isomerase and peptidase loci, restriction fragment length polymorphism (RFLP) fingerprint with probe RG57, metalaxyl sensitivity, and aggressiveness to tomato and potato. The results suggest presence of an asexual population with frequent immigrations from outside the valley. There was a shift of mating type in the population from predominantly A2 to completely A1 in this period. The co-occurrence of mating types was restricted to very few fields in the area around Los Mochis where tomato and potato crops are grown. Genotype variation based on allozyme analysis and mating type was low with only one genotype affecting both crops each year. The genotypes affecting both crops were the only genotypes highly aggressive to both tomato and potato in laboratory aggressiveness tests and the only genotypes widespread on both the tomato and potato crops in the valley each year. These predominant genotypes were highly resistant to the fungicide metalaxyl. Data on metalaxyl sensitivity indicate that allozyme analysis can discriminate between sensitive and resistant isolates in the Del Fuerte Valley. RFLP analysis with the probe RG57 gives further discrimination of genotypes within an allozyme genotype. In the 1995 to 1996 season, four different RFLP genotypes were found within an allozyme genotype. However, there were five other dilocus allozyme genotypes that could not be further split by RFLP analysis in 1995 to 1996 and 1996 to 1997 seasons. Spatial analysis of genotypes suggests that each season individual fields near Los Mochis became infected with one or more genotypes, but only a single genotype, aggressive on both potato and tomato, occurred south and east to the Guasave area.